Systems and methods for unipolar separation of emulsions and other mixtures

ABSTRACT

Embodiments discussed herein relate to systems and methods for separating two or more phases of an emulsion or other mixture. The methods include providing the mixture with a net and unipolar charge (e.g., such that adjacent droplets therein acquire net and unipolar charges), thereby enhancing coalescence of like-phase droplets therein and producing, or enhancing the production of, two or more consolidated phases; and collecting the two or more consolidated phases.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of, and incorporatesherein by reference in its entirety, U.S. Provisional Patent Application61/812,700, filed Apr. 16, 2013, titled “Systems and Methods forUnipolar Emulsion Separation.”

FIELD OF INVENTION

This invention relates generally to separation of two or more phases ofan emulsion or other mixture. In certain embodiments, the inventionrelates to separation of liquid phases in an emulsion or other mixtureby coalescing like-charged droplets.

BACKGROUND OF THE INVENTION

Emulsions appear in a wide range of industries, for example,petrochemical processing, food processing, metal finishing andpolishing, textile, paper, cosmetic, pharmaceutical, biotechnology, aswell as other industries. It is often necessary to perform separationsof one or more components of these emulsions, for example, separation ofan aqueous liquid phase (e.g., water) from a non-aqueous liquid phase(e.g., oil) in an emulsion that is composed of either predominatelyaqueous phase or predominately non-aqueous phase.

For example, in petroleum industries, water is considered a contaminantof the oil products and must be separated from the oil product beforefurther processing, because water may cause considerable corrosion ofthe processing equipment and may affect the life of the equipment, whichmay negatively impact the entire plant. Even trace amounts of water inthe oil may cause serious problems further down the line. In acontrasting example, oils are a common pollutant in downstreamwastewater and byproducts produced in the food and metal industries andshould be separated from the wastewater. Separating oil from water(including trace amounts of oil) is a significant challenge. In order tobe released back into environment, government regulations require thatthe oil does not contain more than certain amounts of oil in the water.The maximum allowed quantity of oil for may be 10 ppm of oil or less.

A significant challenge is to reduce the capital costs of energyconsumption and reduce or eliminate the use of chemical additives(especially those additives that are considered pollutants and/oradditives that otherwise have a negative environmental effect), whichare the traditional method of promoting the breakup of emulsions andother mixtures into their components. Another significant challenge isachieving desired levels of separation of oil and water.

There are a number of traditional methods for separating components ofemulsions. One of the most common separation techniques is gravityseparation. As a primary and low cost treatment step, gravity separationis typically used for separation of emulsions with larger droplet sizes.Gravity separation may be accompanied by a sedimentation process. Forexample, oil may adhere to the surface of solid particles and beeffectively removed by sedimentation. However, gravity separation is noteffective for destabilization of emulsions with small droplet sizes,because the time of sedimentation is impractically long (the requiredtime is roughly inversely proportional to the droplet size squared).

In order to separate emulsions with fine droplets, emulsions aretypically pretreated chemically to promote coagulation and increase flocsize, thereby destabilizing the emulsified phase during gravityseparation. In some conventional methods, the emulsion may also beheated to reduce the viscosity, induce stronger density difference, andreduce the surface tension of the stabilizing films between droplets.Other chemical treatment methods increase the acidity or add ionicagents to the emulsion to neutralize the charge of droplets. Chemicaltreatment methods are energy intensive and may introduce severalundesired chemical contaminants. Separation of the additional chemicalcontaminant may require post-processing unit operations for separationof chemicals, resulting in increased cost and greater risk ofenvironmental pollution.

In addition to gravity separation, other physical methods fordestabilizing emulsions include heating, centrifugation, filtration,ultrafiltration (e.g., using membranes), and reverse osmosis.Ultrafiltration (e.g., membrane ultrafiltration) has a smaller chemicalfootprint than gravity separations and can be somewhat effective foremulsions with small droplet sizes (e.g., smaller than 100 μm). However,the costs associated with ultrafiltration tend to be high (orprohibitive) due to high energy consumption required for ultrafiltrationof large volumes, and due to degeneration of the membrane coatingmaterials over time (e.g., such that new membranes need to be providedon a regular basis, further increasing the costs).

Another physical method for separating components of emulsions iselectrostatic separation. There are three electrostatic body forces thatcan be used to induce coalescence. The electric body force in adielectric liquid, that results from an imposed electric field, can beexpressed as:

$\begin{matrix}{\overset{\rightarrow}{f} = {{\rho_{c}\overset{\rightarrow}{E}} - {\frac{1}{2}{\overset{\rightarrow}{E}}^{2}{\nabla ɛ}} + {\frac{1}{2}{\nabla\left\lbrack {{\overset{\rightarrow}{E}}^{2}{\rho\left( \frac{\partial ɛ}{\partial\rho} \right)}_{T}} \right\rbrack}}}} & (1)\end{matrix}$

where ρ_(c) is volume charge density, ∈ is the fluid permittivity, p isthe fluid density, and T is the fluid temperature. The first term on theright hand side of Eq. (1) is the electrophoretic, or Coulombic, forcethat results from the net free space charges in the fluid. The secondterm, known as the dielectrophoretic force, arises from the permittivitygradient. The last term, called the electrostrictive force, is importantonly for compressible fluids.

In these electrostatic separators, it is primarily the second term,dielectrophoretic force, which is exploited to promote the coalescenceof droplets in the emulsion. In one conventional technique, two parallelplates are immersed in the emulsion with a small gap spacing between theelectrodes. These immersed electrodes are used to induce an externalelectric field to the bulk of the emulsion. The water droplets in themedium become polarized and positive-negative ends attract each other sothat the oil film between two droplets squeezes and is drained. The twoadjacent drops may merge together when the layer of the oil between themis ruptured. These droplets do not acquire a net charge. One limitationof this technique is that the polarization force is scaled with the sizeof droplet. The smaller the droplet size, the larger the field that mustbe applied. Moreover, the orientation of two adjacent droplets isimportant. If the angle is not appropriate, two droplets repel ratherattract and they cannot be merged—this is a significant limitation ofconventional electrostatic separators. The electrohydrodynamic-inducedflow and bi-polar attraction (positive-negative attraction) caused bythe applied electrophoretic force may induce coalescence of droplets.

The electrohydrodynamic flow generated by interactions of the electricfield and fluid flow may also increase the chance of dropletcoalescence. AC and DC fields have been used to establish homogeneous ornonhomogeneous fields between the immersed electrodes. Electrostaticseparators may be effective in separating droplets as small as a fewhundred microns; however, these separators are not effective for smallerdroplet sizes in moderate electrical fields.

Although electrostatic separators show some promise, they also sufferfrom several significant limitations. In conventionalelectrocoalescencers, both electrodes are immersed in the emulsions. Theimmediate consequence is that the technique cannot be reliably used whenthe content of water in the emulsion is high, for example, greater than40 wt. %. The high content of water may limit the level of appliedpotential to the electrodes so that even moderate fields may causeelectrostatic breakdown. Even when the content of water is moderate orlow, the separated water droplets tend to align themselves in thedirection of the imposed field and form a chain-like structure acrossthe gap between the electrodes. The formation of this chain may increasethe chance of electrostatic discharge and arc across the gap. Theelectrostatic discharge poses a risk of explosion, as well as corrosionof the electrode or electrode coatings, and increased contamination dueto chemical decomposition of oil around the electrodes. Moreover, theelectrostatic discharge/breakdown may reduce the rate of coalescence bysuppressing the strength of the background electric field, the rate ofcharging the droplets, and the efficiency of the separator.Additionally, traditional electrostatic separators fail where theaqueous phase has high salt content.

A separation method is needed that is cost-effective, works foremulsions having small droplet size, works irrespective of the saltconcentration of the aqueous phase, and does not pose a risk ofexplosion or require addition of chemical additives to the emulsion.

SUMMARY OF THE INVENTION

Various embodiments of the invention relate to methods and systems forseparating two or more phases of an emulsion or other mixture. Incertain embodiments, the invention introduces a net and unipolar chargeinto the mixture such that adjacent droplets therein acquire net andunipolar charges and, surprisingly, enhance coalescence of like-phasedroplets, thereby destabilizing the mixture and producing, or enhancingproduction of, two or more consolidated liquid phases.

Some embodiments discussed herein provide successful separation of twoor more phases of an emulsion or other mixture despite high conductivityof a dispersed phase, despite high salt content, and/or despite thepresence of a surfactant or other emulsifier. In some embodiments, theconductivity of the mixture is between 1 mS/m to 1 S/m or as high as 10S/m. The systems and methods described herein are applicable to a widevariety of electrical conductivity ranges. Certain embodiments describedherein can separate a variety of mixtures having wide ranges of saltand/or surfactant content without any special adjustment inconfiguration of electrodes or other invasive manipulation.

In one aspect, the invention provides a method for separating two ormore phases of a mixture (e.g., an emulsion), the method including thesteps: (a) providing the mixture with a net and unipolar charge (e.g.,such that adjacent droplets therein acquire net and unipolar charges),thereby enhancing coalescence of like-phase droplets therein andproducing, or enhancing the production of, two or more consolidatedphases; and (b) collecting the two or more consolidated phases.

In certain embodiments, step (a) includes bombarding the mixture withions via corona discharge.

In certain embodiments, step (a) includes providing an emitter electrode(e.g., sharp electrode) and a collector electrode, wherein at least thecollector electrode (e.g., blunt electrode) is in physical contact withthe mixture and a potential difference is applied between the emitterelectrode and the collector electrode at or above a corona dischargethreshold.

In certain embodiments, the emitter electrode is not in physical contactwith the mixture.

In certain embodiments, a gaseous medium (e.g., nitrogen, oxygen, air,argon, helium, etc., or any mixture of different gases) is locatedbetween the emitter electrode and the mixture. In some embodiments, thegaseous mixture is stationary. In some embodiments, the gaseous mixtureis flowing. In some embodiments, the gaseous flow reduces the corrosionof the electrodes because the by-product of the corona discharge becomesless concentrated. In turn, this significantly reduces the maintenancethat needs to be performed for the systems and methods discussed herein.In addition, this increases the useful life of the systems and decreasesoperation costs. The gaseous medium may be at any temperature andpressure.

In some embodiments, ionized gas may be introduced into the mixture.Collapsing bubbles causes ionization of the gas inside the bubbles.

In certain embodiments, the collector electrode is grounded. In someembodiments, the collector electrode is biased with the same polarityabove the ground level. In some embodiments, the emitter electrodeenergy is at +15 kV, the collector electrode may be ground (0 kV) or thecollector electrode can be biased by, e.g., +1 kV.

In certain embodiments, the emitter electrode is a sharp electrode(e.g., a needle, multiple needles, a blade or blades, a thin wire ormultiple wires, etc.).

In certain embodiments, the emitter electrode is coated and/or textured(e.g., coated and/or textured with microstructures, nanotubes (e.g.,CNT), nano-structures, or other sharp geometries).

In certain embodiments, the emitter electrode is made of or coated witha material resistant to ionization-induced corrosion.

In certain embodiments, the collector electrode includes one or moremembers selected from the group consisting of a metal, silicon, and asilicon with native oxide, and/or wherein the collector electrode iscoated with a dielectric film (e.g., and/or wherein the collectorelectrode is a substrate that contains the mixture, e.g., is a channel,pipe, plate, etc.). In some embodiments, the collector electrode is notcoated with a dielectric film, e.g., in some embodiments, the collectorelectrode is bare.

In some embodiments, the potential difference between the mixture andthe emitter electrode is established by applying high voltage to theneedle or by applying high voltage to the mixture by reversing theemitter electrode polarity. In some embodiments, the emitter electrodeis a single electrode (e.g., sharp needle, wire, or engineered surface,or any combination thereof).

In some embodiments, an electric field is applied to the mixture viacontinuous AC or DC discharge or via pulsed discharge. In someembodiments, the discharge is two-phase, three phase, or a multi-phasedischarge with a time-lag discharge. In some embodiments, the dischargeis a direct discharge or a barrier discharge.

In some embodiments, the applied voltage is adjusted based on propertiesof the mixture (e.g., chemical properties, physical properties).

In some embodiments, the mixture is separated during transport (e.g.,transport on a conveyor belt or another conduit).

In some embodiments, step (a) includes providing a portion of themixture with a unipolar charge, the method further comprising mixing thecharged portion of the mixture into the remaining portion of themixture, thereby enhancing coalescence of like-phase droplets thereinand producing, or enhancing the production of, two or more consolidatedphases; and (b) collecting the two or more consolidated phases.

In certain embodiments, step (a) includes injecting, spraying, orotherwise introducing a substance (e.g., liquid droplets, a liquid bath,or a liquid stream) having a net and unipolar charge into the mixture,thereby enhancing coalescence of like-phase droplets therein andproducing, or enhancing the production of, the two or more consolidatedphases.

In some embodiments, the charge is applied to the mixture directly. Insome embodiments, the charge is applied to the mixture indirectly. Insome embodiments, step (a) includes injecting an ionized gas having anet and unipolar charge (e.g., ionized in a separate process, ionizedduring transport to the mixture, ionized via corona discharge in acorona discharge chamber) into the mixture. In some embodiments, theionized gas passes through the mixture. In some embodiments, the size ofthe gas bubbles may be decreased to increase the interface of ionizedgas bubbles with the mixture. In some embodiments, the ionized gas isinjected from a single location into the mixture or from multiple pointsinto the mixture.

In some embodiments, the gas bubbles are injected into the mixture fromthe top (e.g., from above the mixture). In some embodiments, the gasbubbles are injected into the mixture from the bottom (e.g., fromunderneath the mixture).

In certain embodiments, step (a) includes introducing the mixture to asubstrate having a net and unipolar charge (e.g., a substrate with acharge applied via tribo-electrification).

In certain embodiments, the unipolar charge is positive.

In certain embodiments, the unipolar charge is negative.

In some embodiments, the mixture, while maintaining a net and unipolarcharge, includes a combination of species having positive and negativecharges (e.g., which may change over a given time period).

In some embodiments, step (a) includes applying a charge viatribo-electrification during transport of the mixture via a conduit, theconduit comprising a coating configured to improve tribo-electrificationcharging. In some embodiments, wherein step (a) includes applying acharge by direct injection, conduction, induction of net and unipolarcharge, and/or any combination thereof.

In certain embodiments, the mixture includes a plurality of liquidphases.

In certain embodiments, the mixture includes one or more membersselected from the group consisting of particles, proteins, DNA, RNA, andcells (e.g., wherein the mixture includes a stabilizing agent such asparticles or surfactant).

In certain embodiments, the mixture includes a liquid with lowelectrical conductivity (e.g., an insulating liquid or a dielectricliquid, e.g., wherein the low conductivity liquid makes up at least 50wt. % of the mixture). In certain embodiments, the mixture includes aliquid with high electrical conductivity.

In certain embodiments, the mixture includes an aqueous phase, and theaqueous phase has a salt content of at least about 0.5M (e.g., at leastabout 1M, at least about 1.5M, or at least about 2.0M).

In certain embodiments, prior to introduction of the net and unipolarcharge, the mixture includes a phase of droplets having average dropletdiameter less than or equal to about 1000 micrometers in diameter (e.g.,≦500 μm, ≦400 μm, ≦300 μm, ≦100 μm, ≦50 μm, ≦30 μm, ≦20 μm, ≦10 μm, ≦1μm, ≦900 nm, ≦500 nm, ≦300 nm, ≦100 nm, ≦50 nm, ≦30 nm, or ≦10 nm), andwherein the droplets coalesce after introduction of the net and unipolarcharge.

In certain embodiments, the mixture is a two-phase emulsion including anaqueous phase and a non-aqueous phase (e.g., oil), wherein the aqueousphase makes up less than or equal to 50 wt. % of the emulsion (e.g., ≦40wt. %, ≦30 wt. %, ≦20 wt. %, ≦10 wt. %, ≦5 wt. %, ≦3 wt. %, ≦1 wt. %, or≦0.5 wt. %).

In certain embodiments, the mixture is a two-phase emulsion including anaqueous phase and a non-aqueous phase (e.g., oil), wherein thenon-aqueous phase is less than or equal to 50 wt. % of the emulsion(e.g., ≦40 wt. %, ≦30 wt. %, ≦20 wt. %, ≦10 wt. %, ≦5 wt. %, ≦3 wt. %,≦1 wt. %, or ≦0.5 wt. %).

In some embodiments, the mixture is a three-phase mixture. In someembodiments, the mixture includes a liquid phase, a solid phase, and agas phase. In some embodiments, the mixture is a bubble-in-oil mixtureor a foam-in-oil mixture. In some embodiments, the mixture includes anemulsifier (e.g., a surfactant). In some embodiments, the mixtureincludes at least one phase having a salt content at least about 0.5M(e.g., at least about 1M, at least about 1.5M, or at least about 2.0M).In some embodiments, the mixture includes a liquid with high electricalconductivity. In some embodiments, the mixture includes an oil, the oilhaving an electrical conductivity between about 10⁻¹⁴ S/m (highlyinsulating) to about 10⁻⁵ S/m (highly conducting). In some embodiments,the mixture has an electrical conductivity between about 10⁻⁷ S/m toabout 100 S/m.

In some embodiments, the gas pressure and/or the gas temperature iscontrolled/modulated to optimize the quality of the discharge (V-I)characteristics and the breakdown limit (e.g., to increase theelectrical breakdown limit). In some embodiments, the gas pressureand/or the gas temperature is controlled/modulated to optimize theseparation of the mixture (e.g., separation of different phases of anemulsion). In some embodiments, the composition of the gas mixture maybe adjusted to control the V-I characteristics and the breakdown limit.In some embodiments, the gas pressure and/or the gas temperature iscontrolled/modulated to optimize the quality of the discharge (V-I)characteristics and the breakdown limit (e.g., to increase theelectrical breakdown limit) based on sea elevation of a location wherethe separating of the two or more phases takes place.

In another aspect, the invention is directed to a system for separatingtwo or more phases of a mixture (e.g., an emulsion), the systemincluding: (a) a container or support for containing or supporting themixture therein or thereupon, wherein the container or support includes(e.g., is) a grounded collector electrode, and wherein the container orsupport includes a ramp, lip, edge, and/or other elevated portion; (b)an emitter electrode not in physical contact with the mixture; and (c) apower source configured to apply a potential difference between theemitter electrode and the collector electrode at or above a coronadischarge threshold, wherein a gaseous medium (e.g., nitrogen, oxygen,air, argon, helium, etc., or any combination/mixture thereof) is locatedbetween the emitter electrode and the mixture, and wherein the containeror support is configured to permit passage of a first phase of themixture therethrough and/or thereover while disallowing passage of atleast a second phase of the mixture therethrough and/or thereover uponapplication of the potential difference between the emitter electrodeand the collector electrode at or above the corona discharge threshold(e.g., taking advantage of the differential spreading or pumping effectof corona discharge separation), thereby causing or promoting separationof two or more phases of the mixture.

In some embodiments, the electrode (emitter and/or collector) discussedherein are bare. In some embodiments, the electrodes (emitter and/orcollector) discussed herein are coated.

In certain embodiments, the power source is a conventional power source(e.g., a battery, DC power supply, AC power supply, or AC/DC supply. Incertain embodiments, the power source is an electrostatic generator(e.g., a Van de Graaf generator).

In some embodiments, the system is a skimmer, a gravitation separator,or a centrifugal separator. In some embodiments, the system is a skimmerthat has been retrofitted to carry out the separation of the mixture. Insome embodiments, like-charge induced separation can accelerate theseparation process when the mixture is stored in a container.

In some embodiments, the temperature and/or pressure of the gaseousmedium is controlled/modulated, based on sea level elevation of thesystem, to optimize the quality of the discharge (V-I) characteristicsand the breakdown limit (e.g., to increase the electrical breakdownlimit).

In various embodiments, features described with respect to the methodsabove can be applied to the system as well.

The methods and/or systems can perform a pre-treatment step in anexisting system (e.g., a retrofit of a gravitational and/orsedimentation mixture separation process), or they can be combined withother techniques. For example, in some embodiments, methods and systemsdescribed herein may promote coalescence between small droplets to formlarger droplets, which are then more easily handled by traditionalseparation systems (e.g., gravitational, sedimentation, and/or chemicaladditive separation processes).

Elements of embodiments described with respect to a given aspect of theinvention may be used in various embodiments of another aspect of theinvention. For example, it is contemplated that features of dependentclaims depending from one independent claim can be used in apparatusand/or methods of any of the other independent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

While the invention is particularly shown and described herein withreference to specific examples and specific embodiments, it should beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the invention.

FIG. 1 is a schematic drawing demonstrating corona discharge of positiveor negative ions targeting an emulsion interface to promote coalescenceof droplets, in accordance with some embodiments of the invention.

FIG. 2 is a schematic drawing showing a corona discharge system forseparation of two or more phases of an emulsion to simultaneouslypromote droplet coalescence and pumping/spreading effect for phaseseparation, in accordance with some embodiments of the invention.

FIG. 3 is a schematic illustrating a system for spraying unipolarcharged droplets 306 into an emulsion 302 for separation of the emulsionphases, in accordance with some embodiments of the invention.

FIG. 4A shows a series of micrographs of two droplets of deionized waterin silicon oil obtained at various times in relation to contact (t=0) oftwo like-charged (positively-charged) droplets, in accordance with someembodiments of the invention.

FIG. 4B illustrates electrostatic interactions of positively chargedmetal spheres in oil, in accordance with some embodiments of theinvention.

FIG. 4C illustrates electrostatic interactions of like-charge waterdroplets in oil, in accordance with some embodiments of the invention.

FIG. 5 shows experimental data demonstrating conditions for coalescenceof like-charged droplets, in accordance with some embodiments of theinvention. Filled circles denote coalescence and open (unfilled) circlesrepresent non-coalescence of droplets.

FIG. 6A is a graph illustrating coalescence and non-coalescence behaviorof a pair of water droplets carrying different charge magnitudes in oil,in accordance with some embodiments of the invention. The diameters ofdroplets were 1 mm. The separation between droplets was 50 μm. Filledcircles denote coalescence and open (unfilled) circles representnon-coalescence of droplets.

FIG. 6B illustrates non-coalescence of like-charge water droplets, inaccordance with some embodiments of the invention. Droplets wereelectrically connected and positively charged. Non-coalescence behavioris due to the electrostatic repulsion between equally charged waterdroplets.

FIG. 6C illustrates coalescence behavior of positively charged waterdroplets in oil, in accordance with some embodiments of the invention.

FIGS. 7A, 7B. and 7C shows a mechanism that occurs upon coalescence oftwo like-charged droplets in an emulsion, in accordance with someembodiments of the invention. As shown in FIG. 7C, at t=20 microseconds,an electrostatic bridge appears and appears to thicken into a capillarybridge, resulting in coalescence of the droplets.

FIG. 7A illustrates a schematic for a mechanism of like-chargecoalescence of droplets, in accordance with some embodiments of theinvention. Circles correspond to adjacent droplets. Areas 702 correspondto negative charge densities. Areas 704 correspond to positive chargedensity areas.

FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D, illustrate high speed imaging ofinteractions for positively charged droplets in oil for relatively smalland large initial separations, in accordance with some embodiments ofthe invention. A mechanism of like-charge coalescence is presented, inaccordance with some embodiments of the invention.

FIG. 8A illustrates like-charge droplet coalescence after contact att=0, in accordance with some embodiments of the invention. Amounts ofcharges on top and bottom droplets were +35.4 pC and +0.29 pC,respectively. The initial separation of droplets was 50 μm. The scalebar is 0.1 mm in length.

FIG. 8B illustrates like-charge droplet coalescence after contact att=0, in accordance with some embodiments of the invention. Amounts ofcharges on top and bottom droplets were +150 pC and +0.18 pC,respectively. The initial separation of droplets was 320 μm. The scalebar is 0.1 mm in length.

FIG. 8C illustrates like-charge droplet coalescence after contact att=0, in accordance with some embodiments of the invention. Amounts ofcharges on top and bottom droplets were +310 pC and +0.27 pC,respectively. The initial separation of droplets was 415 μm.

FIG. 8D illustrates a schematic for a mechanism of like-chargecoalescence of droplets, in accordance with some embodiments of theinvention. Circles correspond to adjacent droplets. Areas 802 correspondto negative charge densities. Areas 804 correspond to positive chargedensity areas.

FIG. 9 is a schematic for an emulsion separation system 900 using coronadischarge, in accordance with some embodiments of the invention.

FIG. 10 is a schematic for an emulsion separation 1000 system usingcorona discharge, in accordance with some embodiments of the invention.

FIG. 11A illustrates a unipolar electro-coalescence of a system of twoDI water droplets, in accordance with some embodiments of the invention.The applied voltage and current were +7 kV and 1 μA, respectively.

FIG. 11B illustrates a unipolar electro-coalescence of a system of threeDI water droplets, in accordance with some embodiments of the invention.The applied voltage and current were +7 kV and 1 μA, respectively.

FIG. 11C illustrates unipolar separation of an emulsion including 2% byweight of DI water (shown in white color) in Hexadecane (transparentliquid) stabilized with 1.6% by weight surfactant SPAN80® exposed to apositive DC corona discharge, in accordance with some embodiments of theinvention. The applied voltage and corona current were 10.8 kV and 10μA, respectively.

FIGS. 12A and 12B show images of like-charged droplets in an emulsioncharged by corona discharge in bulk oil and 10% water in 90% oil,respectively, compared with images in FIG. 12C where charging wasachieved by tribo-electrification.

FIG. 13 illustrates an experimental corona discharge separator setup1300 for separating emulsions having oil as the main phase, inaccordance with some embodiments of the invention.

FIG. 14A illustrates a water-in-oil emulsion before corona dischargeexposure, in accordance with some embodiments of the invention. The gapspacing between electrode was 10 mm.

FIG. 14B illustrates oil after corona discharge exposure with an appliedvoltage of +7 kV and a current of 1 μA, in accordance with someembodiments of the invention. The gap spacing between electrode was 10mm.

FIG. 15A illustrates water after corona discharge-assisted recovery, inaccordance with some embodiments of the invention.

FIG. 15B illustrates silicone oil recovered from an emulsionelectrostatically, in accordance with some embodiments of the invention.

FIG. 15C illustrates an emulsion used for the corona dischargeseparation process for which the images in FIGS. 15A and 15B are shown,in accordance with some embodiments of the invention.

FIG. 16 illustrates an experimental setup 1600 for separating emulsionswith water as the main phase, in accordance with some embodiments of theinvention.

FIG. 17 illustrates an experimental setup 1700 for direct ion injectioninto emulsions with oil as the main phase, in accordance with someembodiments of the invention.

FIG. 18 illustrates an experimental setup 1800 for separation ofunipolar emulsions and other mixtures, in accordance with someembodiments of the invention.

FIG. 19 illustrates exemplary experimental setups 1900, 1900′, 1901,1901′ for separation of unipolar emulsions and other mixtures, inaccordance with some embodiments of the invention.

FIG. 20 illustrates experimental setups 2000 and 2001 for separation ofunipolar emulsions and other mixtures, in accordance with someembodiments of the invention.

FIG. 21 illustrates an experimental setup 2100 for separation ofunipolar emulsions and other mixtures using tribo-electrificationcharging, in accordance with some embodiments of the invention.

FIG. 22 illustrates experimental setups 2200 and 2201 for introducing acharge to an emulsion or other mixture, in accordance with someembodiments of the invention.

DESCRIPTION

It is contemplated that articles, apparatus, methods, and processes ofthe claimed invention encompass variations and adaptations developedusing information from the embodiments described herein. Adaptationand/or modification of the articles, apparatus, methods, and processesdescribed herein may be performed by those of ordinary skill in therelevant art.

Throughout the description, where articles and apparatus are describedas having, including, or comprising specific components, or whereprocesses and methods are described as having, including, or comprisingspecific steps, it is contemplated that, additionally, there arearticles and apparatus of the present invention that consist essentiallyof, or consist of, the recited components, and that there are processesand methods according to the present invention that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain actions is immaterial so long as the invention remains operable.Moreover, two or more steps or actions may be conducted simultaneously.Embodiments of the invention may be performed as part of a continuous,semi-continuous, or batch process.

It is contemplated that methods of the invention may be combined orsupplemented with reactors, systems, or processes that are known in theart. Any known techniques for material separation, isolation, andpurification may be adapted for application in processes encompassed byvarious embodiments of the invention, for example, techniques fordistillation, extraction, reactive extraction, adsorption, absorption,stripping, crystallization, evaporation, sublimation, diffusionalseparation, adsorptive bubble separation, membrane separation, and/orfluid-particle separation. General information regarding separationprocesses and their design may be found, for example, in “SeparationProcesses,” Klaus Timmerhaus, editor, in The Engineering Handbook,Section VIII, Richard C. Dorf, editor-in-chief, CRC Press, Inc., ISBN0-8493-8344-7, pp. 579-657 (1995). It is also contemplated that methods,systems, and processes of the claimed invention may include pumps, heatexchangers, and gas-, liquid-, and/or solid-phase material handlingequipment known to those of ordinary skill in the field of separations.

The mention herein of any publication, for example, in the Backgroundsection, is not an admission that the publication serves as prior artwith respect to any of the claims presented herein. The Backgroundsection is presented for purposes of clarity and is not meant as adescription of prior art with respect to any claim.

The embodiments described herein apply to separations of emulsions andother mixtures, including for example, (1) a mixture of two or moreliquids that are immiscible, with one liquid phase being dispersed inthe other liquid phase (e.g., oil-in-water emulsions; water-in-oilemulsions; oil-in-saltwater emulsions; saltwater-in-oil emulsions;particle-in-oil mixtures, etc.), where the dispersed phase has aparticle size on the order of 1 nm-1000 nm or 1 μm-1000 μm; (2) gas andoil mixtures (e.g., bubble-in-oil mixtures); (3) foam-in-oil mixtures(e.g., where the foam is formed by coinjecting a surfactant with steamor with a non-condensible gas (e.g., nitrogen, nitrogen and steam); (4)emulsions comprising three phases (e.g., gas, liquid, and solid); (5)multiphase emulsions comprising three or more phases; (6) mixturescomprising any combination of liquids, solids, gases, bubbles, foam,and/or particles.

In some embodiments, the particle size is between 1-5 nm, 1-10 nm, 1-20nm, 20-50 nm, 50-100 nm, 100-300 nm, 300-500 nm, 500-1000 nm. In someembodiments, the particle size is between 1-5 μm, 1-10 μm, 1-20 μm,20-50 μm, 50-100 μm, 100-300 μm, 300-500 μm, 500-1000 μm.

In some embodiments, “saltwater” refers to water having a salinity ofabout 3.5%. In some embodiments, “saltwater” refers to water having asalinity between about 3.1% and about 3.8%. In some embodiments,“saltwater” refers to a brine (e.g., solution of salt (e.g., sodiumchloride) in water) having a salinity between about 3.5% and about 26%at ambient conditions/

In some embodiments, the dispersed phase includes biological material.In some embodiments, the biological material includes biomolecules. Insome embodiments, biomolecules include, but are not limited to, DNA,RNA, cells, enzymes, vaccines, proteins, amino acids, nucleotides,sugars, lipids, etc., whether naturally occurring or artificiallycreated.

In some embodiments, the conductivity of the oil ranges between about10⁻¹⁴ S/m (highly insulating) to 10⁻⁵ S/m (highly conducting). In someembodiments, the conductivity of the water or salty mixture is betweenabout 10⁻⁷ S/m to about 100 S/m.

The emulsion separation methods discussed above may be integrated withexisting skimmers in mixture separation plants. In some embodiments, theemulsion separation methods discussed below can be adapted to anyseparation system as a pre-treatment or post treatment step. In someembodiments, the system for separating emulsions discussed below can beused independently as separate separator.

In some embodiments, the systems and methods for separating emulsionsdiscussed below can be integrated with gravitation separators,centrifugal separators, and the like. In some embodiments, the emulsionsmay be separated (completely or partially) during transport (e.g.,transport on a conveyor belt or similar conduit). In some embodiments,the conveyor belt or conduit includes a texture or coating that helpspromote the separation of the phases in the emulsion.

In conventional methods of electrically induced separation, it isassumed that positive attracts negative (e.g., that a positively chargeddroplet would attract a negatively charged droplet) while like-charge(positive-positive or negative-negative) repels (e.g., that a positivelycharged droplet would repel another positively charged droplet).However, methods are presented herein that apply a unipolar separationtechnique in which droplets of like charge (but different chargedensity) coalesce. Experiments described herein demonstrate that asingle polarity is sufficient to induce coalescence of proximatelike-charged droplets. Therefore, a new class of separators is proposedherein where the droplets coalesce based on like-charge attraction. Boththe emulsion and the droplets are charged.

Without wishing to be bound to any theory, it is postulated that thenon-uniformity of net charge for adjacent droplets causes Coulombicforce. Exploiting Coulombic force induces omni-direction coalescence ofdroplets and eliminates the need for specific orientation for dropletsrespect to the external field. Since there is only one electrodeimmersed in the emulsion, the probability for undesired electrostaticbreakdown can be practically eliminated. Various different embodimentsfall within the unipolar electrostatic separation concept. Examples ofsuch embodiments are described herein. Headers are provided fororganizational purposes and are not intended to be limiting.

Coalescence is an important process in many fluid systems includingraindrop formation, emulsions destabilization, liquid-liquid interfacecontrol in Lab-on-a chip devices, particle ordering in colloidal systemsand atomization and spraying. In some embodiments, the spraying can bedone by an atomizer, spray, electro-spray system, or a fog generatorsystem. In some embodiments, conventional fog generators can be modifiedto generate unipolar charged droplets. Unipolar charged droplets canthen be introduced to the target which could be emulsion/mixture.Electric fields induce coalescence of liquid drops. Theelectro-coalescence of adjacent droplets occurs in important processessuch as storm clouds, dehydration of oil and emulsion breakdown inpetroleum industries, electro-spraying in mass spectrometry, and ink-jetprinting. In these processes, it has been assumed that oppositelycharged masses attract and coalesce while like-charges repel and do notmerge. However, recently it was shown that like-charge conductive hardspheres almost always attract each other when they are close enough butrepel after the contact.

Counter-intuitively, in some embodiments discussed herein, it isdemonstrated that two positively charged water droplets may attract andthen coalesce. The mutual polarization of one droplet induces an imagecharge of opposite polarity on the other droplet causing a short-rangeattractive force. For near droplets with large enough charge difference,this short-range attractive force induces local deformations in bothmeniscuses at the nearest poles. After the meniscuses contact, a liquidbridge is formed between two deformed poles. This transient bridge is aconduit to exchange charge between droplets of like charge to minimizethe electrostatic energy of the system of droplets. Initially, thecurrent carrying liquid bridge is stabilized against the destabilizingeffects of the surface tension through the Maxwell stresses exerted inboth normal and tangential directions on the liquid bridge interface.This electrostatically supported liquid bridge, which is reminiscent ofa “water floating bridge”, temporarily holds two like-charge dropletsconnected. The liquid bridge then reverts to a regular capillary bridgeas the electric field between droplets decreases. The capillary bridgedevelops and tends to minimize the surface of connecting droplets. As aresult, coalescence of like-charge droplets may happen. Coalescence oflike-charge water droplets should particularly influence understandingof emulsion separation.

Short-range attractive force arises due to redistribution of surfacecharge density and mutual polarization of non-equally charged “perfect”conductive spheres, as will be discussed in further detail below. Closeenough like-charge spheres repel each other if they are brought or havebeen brought into contact, since, equipotential conductive spheresalways repel.

As described herein, a droplet with a net and unipolar charge refers toa droplet for which the algebraic summation of negative and positivecharges is non-zero. In certain embodiments, the volume charge densityin a mixture (e.g., an emulsion) can be as small as 1 nC/m³. However, incertain embodiments, it can reach as high as 10 μC/m³ (10⁻⁵ C/m³) whichis around the limitation of oil breakdown. In certain embodiments, thevolume charge density is no less than 10 nC/m³, no less than 100 nC/m³,no less than 500 nC/m³, no less than 1 μC/m³, no less than 5 μC/m³, orno less than 10 μC/m³.

Previous methods that employ polarization forces exhibit a zero netcharge on droplets (number of positive and negative charges are equal),and the volume charge density inside the emulsion/mixture is zero. Anegligible amount of volume charge might be introduced in these systemsaround the electrode, but the whole volume experiences theelectro-neutrality (thermodynamically in equilibrium except the regionsaround the electrodes where the electro-chemical effects cannot beneglected). In contrast to previous methods, embodiments describedherein place the volume in a thermodynamically non-equilibrium statewith non-zero space charge density.

Corona Discharge Bombardment of the Emulsion

In some embodiments, corona discharge may be used to destabilize theemulsion. In one example, a live high voltage wire lost itssolid/oil-insulating jacket. Oil in the jacket spilled over a conductivecountertop while a corona discharge emitted from the bare electrode. Theleaked oil on the countertop expanded, while there was no similar effectobserved on the water meniscus in an adjacent beaker. Corona dischargeapplied a force to the oil, but had no observable effect on a waterinterface. This observation prompted creation of a new separator basedon corona discharge using a well-defined corona discharge set-up.

For example, in certain embodiments, at least two electrodes are used toestablish corona discharge—a sharp electrode (emitter) and a bluntgrounded electrode (collector). The grounded collector electrode is incontact with an oil/water (or other) emulsion, while a gaseous medium islocated between the emitter electrode and the emulsion. In someembodiments, the gaseous medium can be air or other gases, or acombination of different gases and the system works with the gas withina wide range of temperatures and at a wide variety of pressure (e.g.,below, at, or above atmospheric pressure). The embodiments discussedherein may be performed under any temperature and pressure conditions.In some embodiments, temperature and/or pressure may be determined basedon the need for the quality of the discharge. In some embodiments, thebreakdown voltage of the gas in the corona discharge embodimentsdiscussed herein can be adjusted by changing the gaseoustemperature/pressure depending on the elevation of the plant site withrespect to the sea level. When an electric potential difference betweena sharp and blunt electrode is applied above a certain voltage, e.g.,the so-called corona discharge threshold, the imposed electric fieldbecomes strong enough around the sharp tip such that the surroundingneutral gaseous molecules in the electrode separation region becomepartially ionized. A cloud of ions is generated and accelerated towardthe low potential region. The charge is transferred across the gap dueto the drift of charge carriers generated by the electric field.Therefore, the corona discharge is accompanied by a weak electricalcurrent.

Corona discharge establishes a net and unipolar charge in the emulsion.In some embodiments, targeting the emulsion with unipolar ionicbombardment through corona discharge leads to separation of phases. Forexample, in some embodiments, one electrode is immersed in the emulsion,and the other corona discharge electrode is immersed in the air orgaseous medium above the emulsion interface. The gaseous medium may beat any temperature and pressure.

In some embodiments, the emulsion can be a mixture of different liquids,particles and liquids, proteins and DNA, cells, or any matter within aninsulating liquid or dielectric liquid with low electrical conductivity.In some embodiments, the corona electrode is an electrode or systems ofelectrodes with sharp tip or tips. The corona discharge emits from thesharp tip or tips. In some embodiments, the corona discharge electrodecan be a needle, multi-needles with different arrangements, sharp bladeor blades, thin wire or multi-wires, wires coated with microstructures,nano-tubes (CNT) or nano-structures or any other sharp geometries. Insome embodiments, the corona discharge needle is helical, sawtooth, orany other sharp point needle. In some embodiments, the electrode ispreferably constructed from materials that are capable of withstandingthe ionization-induced corrosion, thereby minimizing maintenance costs.In some embodiments, the gaseous medium in which the corona electrode(s)is fixed can be any gaseous medium such as nitrogen, oxygen, air, argon,helium or any other gases or combination of gases, at any pressure ortemperature. In some embodiments, the collector electrode, which isimmersed in the emulsion, can be, for example, a metallic bareelectrode, a silicon substrate with native oxide, a metallic electrodewith dielectric thin film coating, or the like. In some embodiments, thegeometry of the immersed electrode can be planar, a three-dimensional(contoured) surface, a wire or wires, or a mesh, for example. In someembodiments, the immersed electrode can have any geometry or shape.

In some embodiments, the potential difference between the corona emitterelectrode and immersed electrode (which can be grounded or can be atdifferent potential) can be applied by a high voltage power supply. Insome embodiments, at and above a corona discharge threshold voltage, byslightly increasing the voltage, a small current can be measured betweenthe electrodes across the gaseous gap and the emulsion. This is anon-limiting example of a signature of the corona discharge. Anothernon-limiting example of a qualitative signature is an acoustic noisegenerated by the discharge phenomenon, which is sometimes accompanied bya blue-violet glow around the sharp tips. In some embodiments, coronadischarge may or may not accompany with this glow depending on humidityand other factors. Increasing the voltage, one may increase the currentacross the emulsion and increase the volume charge density acquired byemulsion, in accordance with some embodiments of the invention.

In some embodiments, as soon as corona discharge is established, thesize of the droplets begins to grow. In some embodiments, the growthrate is such that after a short period, large droplets can be visuallyobserved in the bulk emulsion. This is evidence of a high rate ofelectro-coalescence. Note that either positive or negative polarity canbe applied to the corona electrode. Choosing positive polarity, however,may increase the electro-dynamic stability of the discharge, inaccordance with some embodiments of the invention.

An important difference between previous techniques and the unipolartechniques described herein is that adjacent droplets in the emulsionacquire net and unipolar charges. Therefore, here, the separation isbased on strong coulombic force between charged droplets. For example,applying positive corona discharge results in droplets with positivecharge, while applying negative corona discharge results in droplets inthe emulsion with negative charge. The sharp electrode(s) is/areseparated from the emulsion interface, and there is no electricalcontact between the emulsion interface and the sharp emitter electrode,in accordance with some embodiments of the invention. Therefore, only asingle polarity electrode is required to be in physical contact with theemulsion, in accordance with some embodiments of the invention. Havingonly one polarity inside the emulsion is advantageous, in accordancewith some embodiments of the invention. In some embodiments, this maysignificantly reduce the chance of electrostatic events, particularlybecause the main voltage drop occurs across the gaseous gap, not withinthe emulsion. Moreover, the amount of charge injected into the emulsionis independent of oil breakdown strengths because the electrode has noohmic contact with the emulsion, and a large volume of charge may belocally injected into the emulsion. This leads to further non-uniformityin the field and an increase in the incidence rate of dropletcoalescence.

Furthermore, in some embodiments, the method can be effective even withhighly conductive emulsions (e.g., where salt concentrations in theaqueous phase are high), since the charge is generated outside of theemulsion. Thus, in some embodiments, the amount of current is primarilydictated by discharge properties in the gaseous gap and is lessdependent on the emulsion. Therefore, the embodiments discussed hereincan be adapted to any oil-water mixture with any quality of oil orwater. It should be noted that the content of salt in water is also notimportant for achieving successful results and desired coalescencelevels.

In some embodiments, coalescence of droplets of salt water solution ofhigh salt content (e.g., >0.5 M, >1.0 M, >1.5 M, or >2 M) can beobserved in an emulsion with silicon oil. Conventionalelectro-coalescencers are designed specifically for quality of oil/waterbased on oil/water and the salt contents—and these can vary region toregion. However, using some embodiments described herein, one cancontrol both applied voltage and current by changing the pressure of thegaseous medium, increasing the voltage at the source, and/or varying thetime of corona exposure to adapt the technique for a desired separationoutput with oil/water emulsions having different qualities (e.g.,different salt contents). The process is easily adapted and controlledfor application to a wide variety of emulsion compositions andseparation needs.

Without wishing to be bound by a particular theory, the mechanism ofunipolar separation appears to follow a newly-discovered phenomenon ofattraction between like-charges in an insulating medium. It has beenspeculated that like-charge particles may attract; however, it hasremained an outstanding question.

Two charged conducting hard spheres almost always attract each other ifthey are close enough. See Lekner, John, “Electrostatics of two chargedconducting spheres,” Proceedings of the Royal Society A: Mathematical,Physical and Engineering Science 468.2145 (2012): 2829-2848,incorporated herein by reference in its entirety. Attractive forcearises due to the mutual polarization of spheres and redistribution ofthe surface charge density over one of these spheres. As two positivelycharged spheres approach closer, one gets a negative charge density atthe pole closest to the other sphere, and then the other acquires anincreased positive charge density at its neighboring pole. Thisattractive force increases without limit as two spheres are approachingtogether. The localized attraction of near charges wins over the overallrepulsion of coulombic force between the two like-charge spheres, andthey attract each other. One theoretical exception to the principlediscussed above is when the two spheres have the same charge ratio thatthey would obtain by being brought into contact. In this case, twospheres repel. Presented herein are applications of this principal inthe coalescence of like-charged droplets having different charge ratiofor separation of phases of an emulsion, as evidenced by experimentalresults presented herein.

Experimental Set-Up and Examples Direct Ion Injection—Corona Discharge

FIG. 1 is a schematic drawing demonstrating corona discharge of positiveor negative ions targeting an emulsion interface to promote coalescenceof droplets, in accordance with some embodiments of the invention. Theschematic 100 on the left shows a schematic drawing of the emulsion 102with a number of droplets 104 dispersed throughout the emulsion 102prior to applying a voltage. The schematic 100′ on the right shows aschematic drawing of the emulsion 102′ after applying the voltage—asseen in this schematic, at least some of the droplets 104 coalescedforming larger droplets 104′. The ionic bombardment due to the coronadischarge may directly inject the created ions into the emulsion volumefrom the interface. The electrification of the emulsion occurs from anexternal source (corona discharge). The ions are generated outside ofthe emulsion and are directly injected into the volume from theemulsion/air interface. The ions distribute in the emulsion and dropletsacquire net charge but with the same polarity. Corona discharge createshighly non-uniform single polarity charges in the emulsion. Withoutwishing to be bound to any given theory, it is believed that thedifference of charge between adjacent droplets causes attraction andeventual merging of droplets. By increasing the time of exposure, theoil can be separated from water by coalescing the small water dropletsand growing the droplet sizes.

FIG. 2 is a schematic drawing showing a corona discharge system forseparation of two or more phases of an emulsion to simultaneouslypromote droplet coalescence and pumping effect or differential spreadingphenomenon for phase separation, in accordance with some embodiments ofthe invention. The schematic 200 on the left is a schematic drawing ofan emulsion 202 with a number of droplets 204 dispersed throughout theemulsion 202 prior to application of corona discharge. The schematic200′ on the right is a schematic drawing of an emulsion 202′ afterapplying corona discharge to the emulsion, which caused at least some ofthe droplets 204 to coalesce and form larger droplets 204′.

In some embodiments, the corona discharge electrode system may bedesigned so that it takes advantage of both (i) the separation of waterdroplets (or other phases) out of the emulsion due to like-chargeelectro-coalescence, and (ii) the physical pumping/spreading/moving ofthe oil-rich phase away from the water-rich phase (or other remainingphase), e.g., out of the emulsion container. Because the ‘pumping’ orspreading effect occurs with oil and not with water, the differentialeffect can be exploited for further separation efficiency, in accordancewith some embodiments of the invention.

In one embodiment, a tank of emulsion is equipped with a protruding edge(ramp) which serves as a low voltage electrode. A sharp electrode ispositioned above the tank and is used to establish the corona discharge.Emulsion may be added to the tank in a continuous, semi-continuous, orbatch-wise manner. The corona discharge from a single or multipleelectrode may physically move or pump the purified oil phase up the rampand direct it to another container or conduit for retaining the purifiedoil separated from the emulsion. The separated aqueous phase may remainin the bottom of the tank where it can be drained.

In some embodiments, one or more of the corona discharge emitterelectrodes are placed around the ramp to exploit the corona dischargepumping effect. While electro-coalescence is occurring inside the bulk,the purified oil is pumped up by an appropriate configuration ofelectrodes. A higher salt content in the aqueous phase of the emulsionmay even be favorable here, since it may enhance the contrastingelectrical conductivities between the oil phase and the aqueous phase,in accordance with some embodiments of the invention.

Unipolar Charge Transfer by Mass Transfer—Spraying Unipolar ChargedDroplets into the Emulsion

In corona discharge embodiments, the charge is introduced directly byionization of gaseous molecules. However, one may deliver unipolarcharges into the bulk emulsion via a charged mass. For example, sprayingunipolar charged drops, or a stream, into an emulsion may result in theemulsion acquiring a net and unipolar charge such that adjacent dropletstherein acquire net and unipolar charges. In some embodiments, sprayingtakes place via electro-spraying or mechanical spraying (e.g.,atomization).

FIG. 3 is a schematic illustrating a system for spraying unipolarcharged droplets 306 into an emulsion 302 for separation of the emulsionphases, in accordance with some embodiments of the invention. Theschematic 300 on the left shows the emulsion 302 with a number ofdroplets 304 dispersed throughout the emulsion 302 prior toelectro-spraying. The schematic 300′ on the right shows the emulsion302′ after electro-spraying, which caused at least some of the droplets304 to coalesce forming larger droplets 304′.

FIG. 3 is a schematic showing a system for spraying unipolar chargeddrops into an emulsion for separation of the emulsion phases. In someembodiments, electrostatic atomization of insulating oil or water may beused and the cloud of small, charged droplets may be directed into theemulsion. In some embodiments, the injected atomized liquid may bechosen based on composition of the emulsion to be separated. Forexample, for a water-in-oil emulsion, where water is the dominant phase,in some embodiments, oil can be atomized. In some embodiments, theliquid droplet with unipolar net charge in the emulsion may transfer thecharge through a conduction and/or convection mechanism to the emulsion.The native water droplets in oil acquire these charges, and themechanism as discussed with corona discharge can occur and cause theelectro-coalescence of unipolar charged droplets. Differentconfigurations of electrodes can be used; for example, circular nozzles,rectangular atomizers, single- or multiple-atomizers can be used.

Pouring Bath of Unipolar Charged Liquid into Emulsion

In another non-limiting embodiment of unipolar charge transfer via masstransfer, an amount of the emulsion is charged first then introducedinto a larger quantity of the emulsion. For example, corona dischargecan be used in some embodiments to inject charge into a bath including aportion of the emulsion. Then, the bath of charged liquid or mixture isintroduced into a larger batch or stream of the emulsion whereseparation is performed. The charged liquid diffuses into the emulsionand transfers charge by both conduction and convection. Unipolar chargetransferred by mass transport and electric conduction may causecoalescence of droplets in the bulk so that the droplet size of thedispersed phase grows. The separated droplets are large enough tosediment and collect in the bottom of the batch. This method can becombined with gravitational separation to expedite the separationprocess. Pure oil can be charged and pour into the gravitationalseparator tanks. The unipolar electro-coalescence occurs due to theunipolar separation.

Tribo-Electrification: Unipolar Separation Technique

In some embodiments, tribo-electrification is used to perform unipolaremulsion separation. This method is an alternative to corona dischargeexposure and spraying of unipolar charged droplets into an emulsion. Itis as simple as the corona discharge technique, but it may eliminate theneed for an active power supply, in accordance with some embodiments ofthe invention.

For example, in some embodiments, a charge is transferred into anemulsion by passing it through a polymer pipe made from PMMA or othertribo-electric material. In some embodiments, the pipe interior surfacemay be coated with a polymer or a combination of polymers such as PMMA,PVC, or the like. Passing the emulsion over the surface may create aunipolar volume charge inside the emulsion due to the friction betweenthe pipe and the emulsion. This unipolar charge may result in anincreased droplet size due to unipolar electro-coalescence. For example,in some embodiments, this concept can be applied to gravitational towerswhere increasing the size of water droplets may cause significantlyfaster separation. In some embodiments, it may be sufficient to simplypass the emulsion over a proper tribo-electric material so that thedroplets become charged. In some embodiments, the gravitational tower,separation column, or other container should be electrically insulatedso that the charge remains in the separator.

Observations

Methods described herein may be combined with current oil/waterseparation processes without substantial changes in their layouts.Existing systems may be retrofitted with a unipolar charge separationstage or module, for example, as described herein.

Demonstrated herein are new separation techniques in which unipolardroplets attract each other. Unlike previous dielectrophoretictechniques, here the active mechanism is electrophoretic force.Experiments verify the like-charge attraction of dispersed droplets in abackground phase. This attraction causes coalescence of droplets,thereby affecting separation of phases of the emulsion. The concept canbe applied to separate droplets in emulsions, as well as solid particlesin suspensions. The applications include, but are not limited to,separation of water/oil emulsions, as well as separation of cells,proteins, DNA, and other kinds of mixtures.

In certain embodiments, only the collector electrode(s) is/are immersedinto the emulsion/mixture, and the emitter electrode is outside theemulsion/mixture. In certain embodiments, the mixture acquires a netcharge. Therefore, unlike the conventional method where volume charge isnegligible, in our method, volume charge is essential, and in certainembodiments it is as at least 1 nC/m³, at least 10 nC/m³, at least 100nC/m³, or at least 1 μC/m³.

An advantage of methods presented herein is that the high voltageelectrode has no contact with the emulsion. Since the main voltage dropoccurs across the gap, the chance of arc or electrostatic breakdown canbe significantly reduced. Moreover, in the embodiments involvingspraying unipolar charged droplets into the emulsion ortribo-electrification of the emulsion, the probability of electrostaticbreakdown is significantly reduced while maintaining unipolar charge inthe bulk.

Another advantage of the proposed method using corona discharge is thatlarge volume charge densities can be injected into the emulsion so thatthere is strong non-uniformity of the electric field in thenon-homogenous emulsion medium. This non-homogeneity in the field maycause potential difference between like-charge droplets and this mayincrease the chance of coalescence. Moreover, in some embodiments,physical separation of water/oil emulsion phases is enhanced by coronadischarge because the purified oil is pumped (or pumping is assisted) bythe electrostatic pressure while the electrostatic pressure on theconductive aqueous phase is zero. This can be a particularly importantembodiment for separation of a mixture in a micro-gravity condition, forexample, where power is limited and a gravitational field is absent.Gravitational separation cannot be used in micro-gravity, while coronadischarge embodiments can be a replacement of such methods. Enhancedcoalescence rate along with a pumping oil phase may result in generationof larger water droplets with lower oil contaminations with minimalpower consumption, even in outer space applications.

Electro-coalescence does not appear to depend on orientation of dropletswith respect to the electric field in the embodiments described herein.In conventional methods, droplets must be oriented in the field so thatattractive force is generated. In those electro-coalescers, smalldeviation of the droplet may cause repulsion between droplets andstabilization rather than the desired separation. In contrast, in theembodiments described herein, electro-coalescence is omni-directional.Direction and orientation is not a requirement since the electrophoreticforce can be exerted in any direction.

Experiments show the effectiveness of the corona discharge systemsdescribed herein for both water-in-oil emulsions and oil-in-wateremulsions. In certain embodiments, phases of emulsions with averagedroplet size <50 microns, <25 microns, <10 microns, <1 micron, <0.5micron or <0.1 micron can be separated. In certain embodiments, therange of applied voltage can be from about 1 to about 20 kilovolts(e.g., a few kilovolts) while the gap spacing between the electrode andinterface of emulsion can be from about 0.1 mm to about 50 mm (e.g., onthe order of tens of millimeters). In some embodiments, the appliedvoltage and the gap can be varied in larger ranges than presented above,but the resulting field should be large enough (˜10⁵-10⁷ Vim) to causecorona discharge from the tip of corona electrode. “Peek's law” mayprovide a first approximation of applied potential for a given gapspacing and a given gaseous pressure and temperature, but the potentialalso depends on the radii of curvature of the corona tip. The coronacurrent and number of corona tips may vary depending on geometry andnumber of tips, but for a single tip the corona current is in the rangeof about 0.1 to about 200 microamp. Increasing the time of exposure maycause enhanced purification, but as little as 1 to 30 seconds issufficient to produce satisfactory coalescence in certain embodiments.The corona discharge separation can also be conducted in multiplestages. At each stage, one may use different corona voltages withdifferent configurations. However, one stage of exposure might beenough.

In certain embodiments, the container for the emulsion, itself, (or aportion thereof) serves as grounded electrode, and can have differentshapes. It can be a flat electrode, an inclined flat electrode, acontoured electrode, or a curved electrode, for example. The emulsioncan be stagnant or it may flow in an open channel.

The electrophoretic forces can collect the purified oil directly or itcan be a dead-end system. The corona discharge exposure can be performedas a pre-treatment step for use in an existing system (e.g., a retrofitof a gravitational and/or sedimentation emulsion separation process), orit can be easily combined with other techniques. For example, the coronadischarge exposure may promote coalescence between small droplets toform larger droplets, which are then more easily handled by currentseparation systems (e.g., gravitational, sedimentation, and/or chemicaladditive separation processes).

In some embodiments, the methods disclosed above can be combined witheach other if required. In some embodiments, these methods can becombined with other traditional techniques, electrostatic existingtechniques, gravitational, filtration or other techniques as pre-stepsor post-process steps depending on required quality of the outputpurified phase and background.

In some embodiments, in order to increase the safety to a requireddegree, one may replace the gaseous phase with any other gases, forexample, inert gasses. The technique is not limited to any particularpressure or temperature of the gas or emulsion, allowing for a moreversatile separation process.

In some embodiments, the method may be applied to cause coagulation ofsolid particles, such as mud, sand, or the like in petroleum or in abiological medium. Similarly, coagulation can be achieved for cells,proteins, DNA, or RNA coagulation (or coagulation of other geneticmaterial) by unipolar charging of a mixture containing such components.

Coalescence of Like-Charged Droplets

FIG. 4A shows a series of micrographs of two droplets of deionized waterin silicon oil obtained at various times in relation to contact (t=0) ofthe two like-charged (positively charged) droplets. Qa is the charge ofdroplet a, Qb is the charge of droplet b, r_(a) is the radius of dropleta and r_(b) is the radius of droplet b. Attraction of droplets andcoalescence is observed where the charge densities of the droplets aredifferent, e.g., for example where Qa/ra>>Qb/rb, and where the dropletsare sufficiently close to each other.

FIG. 4B presents the experimental results for electrostatic interactionbetween two positively charged isolated metal spheres of the same sizeat close separations. It was observed that the positively chargedspheres attract each other when the difference in magnitude of thecharge between the spheres is large enough. As the charge difference isestablished, the attractive force pulls the right sphere towards thefixed sphere on the left. After a brief contact, the two spheres becomeequipotential and then repel each other. This observation confirms arecent prediction for attraction of conductive hard spheres carryinglike-charges and the repulsion after the contact.

FIG. 4C shows a series of micrographs of electrostatic interaction oflike-charge water droplets of different size carrying positive chargesin a bath of oil with sufficiently large charge differences. The chargesat the top and bottom droplets were +10.7 pC and 0.94 pC, respectively.Similar to metal spheres discussed in relation to FIG. 4B, twonon-equipotential droplets with a large enough charge difference attractat close separations. However, after the contact at t=0, unlike themetal spheres of FIG. 4B, two droplets attract each other and coalesceas shown in FIG. 4C. Like-charge droplets slowly approach, andcoalescence occurs immediately after the apparent contact at the nearestpoles. The scale bar shown in FIG. 4C is 0.5 mm. The background oil is450 centistokes silicone oil.

FIG. 5 presents experimental data showing that coalescence of twolike-charged droplets occurs when Coulombic force (FAtr/FRep) isroughly >1. Where the magnitude of the difference in like chargesbetween the two droplets is greater (e.g., where Qa/Qb is higher),coalescence is observed between droplets at greater distances from eachother, up to about 1 mm apart.

FIG. 6A depicts the result of charge measurements for two positivelycharged near droplets of the same size at a fixed initial separation of50 μm. The initial separation is the gap between the neutral dropletsbefore charging. As it is shown in FIG. 6A, a small charge differencebetween droplets is enough to cause electro-coalescence of dropletsaccording to some embodiments of the invention.

In contrast, FIG. 6B illustrates that for two electrically connectedidentical water droplets, it is observed in some embodiments thatdroplets do not merge even if they are mechanically pushed together.This is attributed to the fact that the droplets become equipotentialupon contact and the charge difference then equals zero. For identicalspheres, a=b, the expression for the short-range attractive forcebetween like-charge conductive spheres with net positive charges ofQ_(a) and Q_(b) was obtained as

$\begin{matrix}{F_{Atr} = {- \frac{\left\{ {Q_{a} - Q_{b}} \right\}^{2}}{8{\pi ɛ}_{0}\alpha \; S\left\{ {{\ln\left( \frac{4\alpha}{S} \right)} + {2\gamma}} \right\}^{2}}}} & (2)\end{matrix}$

∈₀, S and γ are medium permittivity, the separation between droplets andEuler's constant, respectively. From Eq. (2) above, it can be inferredthat close enough spheres of the same size always attract if and only ifQ_(a)≠Q_(b). Whereas, for two identical spheres with precisely the samecharges, a=b and Q_(a)=Q_(b), the attractive force is zero. In thiscase, equally charged spheres become equipotential and repel. Forequipotential spheres at close separations, the repulsive force,F_(rep), is independent of the separation and can be obtained byKelvin's formula:

$\begin{matrix}{F_{rep} = {{- \frac{1}{4{\pi ɛ}_{0}}}\frac{Q_{\alpha}^{2}}{\left( {2\alpha} \right)^{2}}\frac{{4\mspace{11mu} \ln \mspace{11mu} 2} - 1}{6\left( {\ln \mspace{11mu} 2} \right)^{2}}}} & (3)\end{matrix}$

Although the experimental results shown in FIGS. 6A, 6B, and 6C can beinterpreted by the expression for attraction of like-charge presented inEq. (2) above, it is still not clear why the unequally charged dropletscoalesce after contact. In order to investigate the mechanism ofcoalescence, a high-resolution high speed imaging of droplet coalescencewas performed immediately before and after contact.

FIGS. 7A-7C show a mechanism that occurs upon coalescence of twolike-charged droplets in an emulsion. At t=20 microseconds, anelectrostatic bridge appears, and, without wishing to be bound to anyparticular theory, appears to thicken into a capillary bridge, resultingin coalescence of the droplets.

FIGS. 8A, 8B, and 8C illustrate the behavior of like-charge DI waterdroplets in silicone oil in a series of sequential high-speed images at180,000 frames s⁻¹. For two neighboring like-charge droplets, thedroplet with larger absolute positive charge (top droplet) polarizes theother droplet with smaller net positive charge (bottom droplet). FIG. 8Drepresents a cartoon of electrostatic interactions for attraction andcoalescence of like-charge droplets. The cartoon is based onexperimental visualizations presented in FIGS. 8A-8C.

As shown in FIG. 8D, the batch of negative image charge (gray cloud)appears at the nearest pole of the droplet with smaller positive charge(pink cloud). The electric field between poles of nearby dropletsincreases as a result of local charge redistribution. The attractionbetween the positively charged meniscus and its negative image charge onthe nearest pole of the other droplet meniscus causes attraction betweendroplets.

As can be seen in FIGS. 8A, 8B and 8C the attractive force inducesTaylor cone-like deformation due to local enhancement of Maxwellstresses in the nearest poles where the electric field is strong. Bothdroplets and the two deformed meniscuses approach together. As the twomeniscuses approach, the electric field becomes even stronger, and theenhanced field redistributes the charge and its image causing morepronounced deformations in the meniscuses. The deformed meniscusesfinally touch each other, and a liquid bridge is immediately formedbetween the two droplets.

For droplets with small separations as presented in FIG. 8A, theformation of the bridge immediately after contact leads to high localcurvature of the neck between connecting like-charge drops. Theformation of the curved neck creates a local low-pressure regionresulting in an inward flow towards the bridge. The inward flow suppliesliquid to the bridge and fattens the neck; thus, the coalescence oflike-charge droplets proceeds. For such small separations, the bridgemorphology at its early evolution, t=0, cannot be captured with a properoptical resolution due to its small sizes. In order to visualize thedetails of evolution with reasonable resolutions after the contact, theinitial separation between the droplets was increased as can be seen inFIGS. 8B and 8C In order to establish the like charge attraction andcoalescence for the new larger separations, the absolute magnitude ofthe charge and the charge difference between drops were increased. Thecharge on the top droplet was increased near its Rayleigh limit whilethe charge on the bottom droplet was kept small. For these largerinitial separations, the electro-coalescence also happens. It wasobserved that the two droplets attract each other and their meniscusesare deformed at their nearest poles. As the two deformed meniscusescontact, a remarkably stable transient liquid bridge is formed. The highaspect ratio liquid bridges clearly differ from the conventionalcapillary bridges. Such transient liquid bridges are reminiscent of thepreviously reported floating water bridges in air and the electricallysupported high aspect ratio columns of slightly conductive liquids.Similar to the water floating bridge, since the permittivity of theliquid bridge is larger than the permittivity of the medium (oil in ourcase), ∈_(w)>∈_(o), the current carrying liquid bridge is stabilized bythe normal and tangential electrostatic Maxwell stresses in the bridge.Both electrostatic and polarization force tends to “level” the bridgeagainst the destabilizing effects due to the surface. Such stable liquidbridge holds two droplets electrically connected. Initially, when theelectric field across the bridge is large, the liquid bridge between twocharged droplets is stabilized by the electric field. As the chargetransfers across the bridge, the tangential field between oil/waterinterfaces along the bridge gradually decreases. Subsequently, theelectrostatically supported bridge reverts to capillary bridge. Acapillary bridge between connecting droplets tends to minimize thesurface of the connecting bodies. The formation of a self-sustainedcurrent carrying bridge and its transformation to capillary bridge favorthe coalescence of two connecting droplets. For highly chargedneighboring droplets, before the meniscus contact, electro-sprayingoccurs due to the intense tangential stresses exerted to the deformedpole. Even in the presence of such cone-jetting and electro-sprayingbetween highly charged droplets, the like-charge coalescence proceeds.This implies that coalescence of like-charges is a general phenomenonand it may happen for wide ranges of charge magnitudes.

FIGS. 9 and 10 show two example schematics of oil/water emulsionseparation systems that employ like-charged droplet coalescence asdescribed herein.

In FIG. 9, an emulsion flows in a half pipe 902 below a corona wire(emitter electrode) 904. In some embodiments, the half pipe 902 maycontain or may itself be a grounded collector electrode. The separationoccurs during flowing of the emulsion along the half pipe 902.Differential spreading/pumping of the oil phase as a result of coronadischarge forces the oil phase over the edge of the half pipe 902, anddown a collector ramp 906 into a collection vessel 908. Instead of ahalf pipe 902, another channel of different geometry could be used, forexample. In certain embodiments, multi-branch half pipes can be used,equipped with corona wires above the emulsion/air interface.

In the embodiment shown in FIG. 10, an emulsion fills a tank 1010. Acorona wire 1004, corona blade, or any other type of sharp emitterelectrode is placed above the tank near a ramped or tilted side or lip1012 of the tank 1010. Differential spreading/pumping of the purifiedoil phase results from the corona discharge and forces the oil phase(and not the water phase) over the lip and into a collection vessel1008. In some embodiments, the tank may be filled constantly withemulsion while corona discharge separates the phases and the pure oil iscollected. Alternatively, in some embodiments, the tank may operate inbatch mode or semi-batch mode. For large scale systems, in someembodiments, multiple high voltage electrodes can be used.

In some embodiments, tribo-electrification is used instead of coronadischarge to produce the unipolar conditions leading to separation ofthe phases of the emulsion.

The concept of like-charge coalescence can be applied to thedestabilization of emulsions. FIGS. 11A, 11B and 11C demonstratelike-charge coalescence for a system of two water drops in oil and awater-in-oil emulsion. FIGS. 11A and 11B show the unipolar coalescenceof systems of two and three neighboring water drops in oil subjected tounipolar ion injection, respectively. A positive DC corona discharge wasestablished by applying high voltages above the corona dischargethresholds to a sharp emitter electrode. The air adjacent to the emitterelectrode was ionized, and a cloud of positive ions was acceleratedtowards the air/liquid interface due to the strong electric field. Theaccelerated positive ions were injected into the oil volume. Theinjected charge was deposited over the surface of the water/oil dropletinterface. Since the acquired net charge by the water droplets wasproportional to their surface areas, an arbitrary charge differencebetween two neighboring droplets with different size may be establishedby applying non-uniform charge injection. Once enough of a chargedifference is established, short-range attraction may cause coalescenceof like-charge water drops.

FIG. 11C shows like-charge coalescence and unipolar separation of anemulsion comprised of 1.5% wt. DI water in Hexadecane subjected to acorona discharge with different exposure times. In order to stabilizethe emulsion, 1.6% wt. Surfactant Span80® was added. The mean diameterof droplets in emulsion was measured to be about 300 nm right before theionic exposure. The 20 ml of the emulsion poured in two identicalbeakers. The left beaker was exposed to a corona discharge while theright beaker was left with no exposure. Continuous exposure of theemulsion to the discharge supplies spatially non-uniform volume chargedensity to the adjacent water droplets. The adjacent water dropletsacquire non-uniform positive charge, which promotes like-chargecoalescence of water droplets in oil. As a result, the size of thedroplets increased as they were exposed to the discharge and theemulsion separation occurred. As shown in FIG. 11C, the cloudy emulsionin the left beaker turned to transparent oil as the water droplets werecoalesced and settled down. In the absence of exposure, the cloudyappearance of the right beaker showed negligible change during the sametime of experiments suggesting that the coalescence of droplets wasminimal as the emulsion was stable during the experiments.

FIGS. 12A, 12B, and 12C show images of like-charged droplets in anemulsion charged by corona discharge, compared with charging bytrio-electrification. In order to obtain the tribo-electrificationresults presented in FIG. 12C, PMMA substrate was rubbed with polyesterfiber. Other pairs of materials can be used to produce the chargedsubstrate onto which the emulsion is poured or otherwise introduced.Deposition of emulsion on un-rubbed substrates produces no separationeffect since the charge is absent over the substrate. Upon rubbing thedry PMMA substrate, the substrate becomes positively charged while thefiber becomes negative. The charge over the substrate reached asaturation limit and was measured to be ˜100 nC/m². Depositing theemulsion on the charged substrate resulted in vigorous separation of theemulsion. A small charge difference between two neighboring dropletscauses an attractive force, which causes coalescence of the waterdroplets. Small charge differences in a dense emulsion may result indestabilization of the emulsion and the desired separation of thephases. These charges can be unipolar on two or many droplets. Withoutwishing to be bound to any particular theory, a single polarity ofcharge is sufficient to induce emulsion separation.

Separation of 25% Water-75% Oil

In this example, corona discharge assisted separation of an emulsion wasconducted in the presence of electrostatic pumping of the separated oil.As shown in FIG. 13, a curved electrode 1314 was first filled with anemulsion of DI water in Silicone Oil (25 wt. % water, 75 wt. % oil)1316. The curved electrode 1314 was grounded. A corona needle 1318 wasfixed above the emulsion/air interface. The distance between the coronaelectrode and emulsion interface was tens of millimeters. Therefore, thegrounded electrode 1314 had contact with the emulsion 1316 while thecorona needle 1318 was located in ambient air and had no ohmic contactwith the emulsion 1316. By applying voltage to the needle 1318 above acritical value, a positive corona discharge was established over surfaceof emulsion 1316 and curved grounded electrode 1314. The coronadischarge establishment was confirmed by measuring the corona current.

The cloud of ionized air accelerated toward the emulsion 1316 in thepresence of the strong electric field and the emulsion 1316 waspositively charged with such ionic bombardment. The water droplets inthe bulk oil immediately coalesced. Without wishing to be bound to atheory, non-uniform charging of the droplet is believed to beresponsible for coalescing of positive-positive charged droplets.Moreover, the pure separated oil by corona discharge exposure climbed upthe curved ramp on the right side of the curved grounded electrode 1314.Corona discharge was used to both separate and pump the pure oil out ofthe emulsion container 1320. It should be noted that only pure oil couldclimb up the ramp 1322, while water was not affected. Systems thatexploit this differential effect may be implemented, further enhancingseparation of phases of the emulsion. The electrostatic pressure cannotbe developed over a water droplet, and water (or other aqueous phase)cannot move up the ramp 1322. This is believed to be because theelectrical conductivity of water is too high, and the charge relaxationis fast. Therefore, the electrostatic pressure cannot be establishedover water droplets and pump them up. In contrast, for background oil,charge may stay for a long period of time and electric pressure can beestablished and pump the separated pure oil up the ramp.

Corona discharge of 7 kV-1 μA was applied (7 milliwatt powerconsumption) for about 10 seconds over the air-emulsion interface to thewater-in oil emulsion as can be seen FIG. 14A. FIG. 14B illustrates thatthe small droplets showed vigorous electro-coalescence. About 90% of theoil content was recovered at this stage. The recovered oil was clear butwith minor tracks of water micro-droplets. The purified oil with minortrack of water droplets was transferred to the third stage. With 20seconds of sequential discharge 7 kV-1 μA and then stronger discharge8.6 kV-2 μA and much stronger 12 kV-3 μA, the accomplished separationshows a separation of 99.9%. The energy consumption for coronadischarge-assisted separator with a single needle electrode can be aslow as a few miliwatts for lab-size separations. In many embodiments,methods and systems described herein can be used to scale up. Forexample, with only 40 watt hours (10 kV, 1 μA), one may process 0.1 m³per/hour.

FIG. 15C illustrates an emulsion used for the separation process. FIG.15B shows silicone oil recovered from the emulsion electrostatically.FIG. 15A illustrates water after corona discharge-assisted recovery.

Separation of 90% Water-10% Oil

Setup 1600 shown in FIG. 16 demonstrated corona discharge separation ofthe emulsion without exploiting the pumping effect. The coronadischarge-assisted technique can be used to separate water out ofpredominately-oil emulsions, where the emulsion contains lowconcentrations of water and/or small droplet sizes of water emulsifiedin the oil background. In other embodiments, the coronadischarge-assisted technique can be used to separate water and oilphases from emulsions that are predominately water.

The corona discharge exposed emulsion tends to minimize itselectrostatic energy when exposed to the discharge. Therefore, the ionsmay transfer the oil droplet towards the substrate. If the substrate isoleophilic, the oil creates a thin film below the liquid volume. Thedivergent electric field may drag the oil out of the droplet and causethe water to become separated. It should be noted that when the oil isemulsified in water, the capacitance of the system is large. The chargedoil layers are far from the low potential substrate. As the field isexposed, the cloud of ions reaches the water interface and passesthrough the interface. The oil droplets are now attracted to thesubstrate to make the capacitance as low as possible. The coronadischarge-assisted technique makes separation possible even foremulsions with a fraction of 1% oil in the water. The technique showspromise, particularly where the substrate is flat. The technique seemsto be more efficient when implemented in droplet-wise form.

Ion Injection

In the configuration depicted in FIG. 17, the droplets 1730 are directlycharged in a bath of emulsion by unipolar ion injection through a coronaneedle 1718 similar to the embodiment shown in FIG. 13. However, becausethe container 1720 is not curved, the oil cannot be pumped up. Theseparated oil stays on the top and is not pumped out by coronadischarge. After coalescence, the phases may be separated using standardprocesses.

In one example, a quartz container was used. The quartz container wasfilled with the emulsion (10% oil-90% emulsion stabilized by Span® 80nonionic surfactant). A grounded flat electrode 1714 was fixed at thebottom of the container 1720 as shown in FIG. 17. A corona needle 1718was fixed above the emulsion/air interface. The gap between theelectrode and emulsion/air interface was about 5 mm. The groundedelectrode 1714 was a silicon substrate with a native oxide. Byincreasing the applied voltage, the electric current across the emulsionremained zero and emulsion did not destabilize. Further increasing theapplied voltage, at and above the onset of corona discharge threshold,the current was established. This is the signature of the coronadischarge. Above this threshold voltage, immediate coalescence betweenwater droplets 1730 was observed, and phase separation (emulsiondestabilization) took place. In this example, 7 kV was applied and thetotal current at this voltage was 0.9 μA. The mean diameter of waterdroplets 1730 in oil before separation was 50 μm. After corona dischargeexposure, depending on exposure time, the mean droplet size grew anorder of magnitude larger.

Constructive Example Charging a Portion of Emulsion and Mixing ChargedPortion with Neutral Emulsion

As shown in FIG. 18, a water in oil emulsion is split up between twocontainers (or the emulsion or other mixture may initially be present intwo containers). A first portion of the emulsion or other mixture isplaced into a container 1820. The emulsion 1816 is charged by coronadischarge. A corona needle 1818 and a grounded electrode 1814 withdielectric coating are used to establish the corona discharge, asdiscussed in some embodiments above. The grounded electrode 1814 is incontact with the emulsion 1816. A gaseous medium (e.g., one gas or amixture of gases discussed above, at any pressure and temperature) islocated between the emulsion 1816 and the corona needle 1818. When anelectric potential difference between the corona needle 1818 and thegrounded electrode 1814 is applied (e.g., by continuous AC or DCdischarge or pulsed discharge) above a corona discharge threshold, theimposed electric field becomes strong enough around the sharp tip of thecorona needle 1818. such that the surrounding neutral gaseous medium inthe electrode separation region become partially ionized, creating acloud of positive ions 1840, which charges the emulsion 1816. Thecharged emulsion 1816′ is then transported via a conduit 1842 to asecond container 1844. The second container includes initially neutralemulsion 1846. The charged emulsion 1816′ may then be mixed with theinitially neutral emulsion 1846 that needs to be separated.

Constructive Example Experimental Setups Using Different EmitterElectrode and Grounded Electrode Configurations

Referring now to FIG. 19, the experimental setup 1900 employs multipleemitter electrodes 1918 and a grounded electrode with dielectric coating1914. The experimental setup 1900′ employs multiple emitter electrodes1918 and a bare grounded electrode 1914′. The experimental setup 1901employs a single wire emitter electrode 1918′ and a grounded electrodewith dielectric coating 1914. The experimental setup 1901′ employs asingle wire emitter electrode 1918′ and a bare grounded electrode 1914′.

Constructive Example Experimental Setups Applying Corona DischargeDuring Transport of an Emulsion or Other Mixture

Referring now to FIG. 20, experimental setups 2000 and 2001 areillustrated. Experimental setup 2000 illustrates applying coronadischarge during transport of a water in oil emulsion 2016 (othermixtures may be separated as well). A corona discharge wire 2018′ isplaced above the emulsion 2016 (e.g., the corona discharge wire 2018 isnot in contact with the emulsion 2016). In some embodiments, the coronadischarge wire 2018′ is coated. In some embodiments, the coronadischarge wire 2018′ is bare. Half (or another suitable portion of thepipe volume) is filled with gas (e.g., air or any gas composition thatmay effectively increase the effect of current discharge). Theexperimental setup 2000 allows for an emulsion 2016 (or another mixture)to be separated during transport using corona discharge. Any suitablecorona discharge electrode geometries may be used.

Experimental setup 2001 illustrates applying corona discharge duringtransport of a water in oil emulsion 2016′ (other mixtures may beseparated as well). Multiple corona electrodes 2018 are placed above theemulsion 2016′. Half (or another suitable portion of the pipe volume) isfilled with gas (e.g., air or any gas composition, including mixtures ofdifferent gases, that may effectively increase the effect of currentdischarge). The experimental setup 2001 allows for an emulsion 2016′ (oranother mixture) to be separated during transport. Any suitable coronadischarge electrode geometries may be used.

Constructive Example Tribo-Electrification Charging Exemplary Setup

Referring now to FIG. 21, an experimental setup 2100 for separating anemulsion or another mixture during transport is shown. Charge can beintroduced to the moving emulsion 2116 by tribo-electrification chargingduring transport. As shown in FIG. 21, an emulsion 2116 may be separatedduring transport in a pipe 2150 (or any other conduit capable oftransporting an emulsion or another mixture). The interior surface ofthe pipe 2148 (e.g., the surface that is in contact with the emulsion orother mixture being transported) is coated with a tribo-electric coatingthat is configured to improve tribo-electrification charging. In someembodiments, the coating 2150 includes a combination of Teflon and Nylon(in suitable proportions). In some embodiments, the coating 2150 is astatic coating of a suitable type (e.g., suitable for improvingtribo-electrification charging). Unipolar charge in the volume of themixture can promote the separation of the emulsion 2116 during thetransport as it passes through the pipe 2150. Unipolar separation can becompleted completely or in part during the transport of the emulsionthrough the pipe 2150.

Constructive Example Ionized Gas Exemplary Setup

Referring now to FIG. 22, an experimental setup 2200 for separatingemulsions or other mixtures is shown. Neutral gas (e.g., gas having nonet charge) 2254 is fed into an ionization chamber 2256. The neutral gas2254 is then ionized in the ionization chamber 2256. In someembodiments, the neutral gas 2254 is ionized by using corona discharge(e.g., as discussed for other corona discharge embodiments above). Thepartially ionized gas 2254′ carrying a unipolar charge is thenintroduced into an emulsion or other mixture 2216 (e.g., from onelocation or from multiple locations). In some embodiments, the partiallyionized gas 2254′ passes through the emulsion or other mixture 2216.

The experimental setup 2201 illustrates another illustrative embodimentfor introducing a charge to an emulsion or another mixture 2217 to beseparated. Neutral gas 2255 is fed into a pipe or another conduit 2258.The neutral gas 2255 is ionized during transport through the pipe oranother conduit 2258 (e.g., ionized via corona discharge). Partiallyionized gas 2255′ is then injected into the emulsion or another mixture2217 (from a single location or from multiple locations). In someembodiments, the partially ionized gas 2255′ passes through the emulsionor other mixture 2217.

In some embodiments, to increase the interface of the ionized gasbubbles with the emulsion or other mixture 2216 or 2217, the size of thebubbles can be decreased. In some embodiments, the emulsion or othermixture 2216 or 2217 can be physically agitated prior to the entrance ofthe bubbles into the emulsion or other mixture 2216 or 2217. The bubblescan be injected into the emulsion or other mixture 2216 or 2217 from asingle location or from multiple locations. The bubbles may be injectedfrom underneath the emulsion or other mixture 2216 or 2217. In otherembodiments, the bubbles may be injected from above the emulsion orother mixture 2216 or 2217.

Other Embodiments

Embodiments and examples described herein are for illustration purposeonly not for limitation. The scope of the invention is illustrated bythe claims attached hereto and various changes and modifications withinthe scope of the invention will be apparent to those skilled in the art.

1. A method for separating two or more phases of emulsion mixture, themethod comprising the steps of: (a) providing the mixture with a net andunipolar charge, thereby enhancing coalescence of like-phase dropletstherein and producing, or enhancing the production of, two or moreconsolidated phases; and (b) collecting the two or more consolidatedphases.
 2. The method of claim 1, wherein step (a) comprises bombardingthe mixture with ions via corona discharge.
 3. The method of claim 2,wherein step (a) comprises providing an emitter electrode and acollector electrode, wherein at least the collector electrode is inphysical contact with the mixture and a potential difference is appliedbetween the emitter electrode and the collector electrode at or above acorona discharge threshold.
 4. The method of claim 3, wherein theemitter electrode is not in physical contact with the mixture.
 5. Themethod of claim 4, wherein a gaseous medium is located between theemitter electrode and the mixture.
 6. The method of claim 3, wherein thecollector electrode is grounded.
 7. The method of claim 3, wherein theemitter electrode is a sharp electrode.
 8. The method of claim 3,wherein the emitter electrode is coated and/or textured.
 9. The methodof claim 3, wherein the emitter electrode is made of or coated with amaterial resistant to ionization-induced corrosion.
 10. The method ofclaim 3, wherein the collector electrode comprises one or more membersselected from the group consisting of a metal, silicon, and a siliconwith native oxide, and/or wherein the collector electrode is coated witha dielectric film.
 11. The method of claim 3, wherein the potentialdifference between the emitter electrode and the mixture is establishedby applying a high voltage to the emitter electrode or by applying ahigh voltage to the mixture by reversing a polarity of the emitterelectrode.
 12. The method of claim 3, wherein an electric field isapplied via continuous AC or DC discharge or via pulsed discharge,wherein the discharge is a two-phase, three-phase, or multi-phasedischarge and/or wherein the discharge is a direct discharge or abarrier discharge.
 13. (canceled)
 14. (canceled)
 15. (canceled)
 16. Themethod of claim 1, wherein the separating is carried out duringtransport of the mixture.
 17. The method of claim 1, wherein step (a)comprises providing a portion of the mixture with a unipolar charge, themethod further comprising mixing the charged portion of the mixture intothe remaining portion of the mixture, thereby enhancing coalescence oflike-phase droplets therein and producing, or enhancing the productionof, two or more consolidated phases; and (b) collecting the two or moreconsolidated phases.
 18. The method of claim 1, wherein step (a)comprises injecting, spraying, or otherwise introducing a substancehaving a net and unipolar charge into the mixture, thereby enhancingcoalescence of like-phase droplets therein and producing, or enhancingthe production of, the two or more consolidated phases.
 19. The methodof claim 1, wherein step (a) comprises injecting an ionized gas having anet and unipolar charge into the mixture.
 20. (canceled)
 21. The methodof claim 18, further comprising agitating the mixture prior to step (a).22. The method of claim 1, wherein step (a) comprises introducing themixture to a substrate having a net and unipolar charge that is positiveor negative.
 23. (canceled)
 24. (canceled)
 25. The method of claim 1,wherein the mixture, while maintaining a net and unipolar charge,comprises a combination of species having positive and negative charges.26. The method of claim 1, wherein step (a) comprises applying a chargevia tribo-electrification during transport of the mixture via a conduit,the conduit comprising a coating configured to improvetribo-electrification charging.
 27. The method of claim 1, wherein step(a) comprises applying a charge by direct injection, conduction,induction of net and unipolar charge, and/or any combination thereof.28. The method of claim 1, wherein the mixture comprises a plurality ofliquid phases and/or wherein the mixture comprises one or more membersselected from the group consisting of particles, proteins, DNA, RNA, andcells, and/or wherein the mixture comprises a liquid with low electricalconductivity.
 29. (canceled)
 30. (canceled)
 31. The method of claim 1,wherein the mixture comprises an aqueous phase, and the aqueous phasehas a salt content of at least about 0.5M.
 32. The method of claim 1,wherein, prior to introduction of the net and unipolar charge, themixture comprises a phase of droplets having average droplet diameterless than or equal to about 1000 micrometers in diameter, and whereinthe droplets coalesce after introduction of the net and unipolar charge.33. The method of claim 1, wherein the mixture is a two-phase emulsioncomprising an aqueous phase and a non-aqueous phase, wherein the aqueousphase is less than or equal to 50 wt. % of the emulsion and/or whereinthe non-aqueous phase is less than or equal to 50 wt. % of the emulsion.34. (canceled)
 35. The method of claim 1, wherein the mixture is athree-phase mixture.
 36. The method of claim 1, wherein the mixturecomprises a liquid phase, a solid phase, and a gas phase.
 37. The methodof claim 1, wherein the mixture is a bubble-in-oil mixture or afoam-in-oil mixture and/or wherein the mixture comprises an emulsifier.38. (canceled)
 39. The method of claim 1, wherein the mixture comprisesat least one phase having a salt content of at least about 0.5M. 40.(canceled)
 41. The method of claim 1, wherein the mixture comprises anoil, the oil having an electrical conductivity between about 10⁻¹⁴ S/m(highly insulating) to about 10⁻⁵ S/m (highly conducting).
 42. Themethod of claim 1, wherein the mixture has an electrical conductivitybetween about 10⁻⁷ S/m to about 100 S/m.
 43. The method of claim 5,wherein the gaseous medium is flowing.
 44. The method of claim 5,further comprising modulating the gaseous medium temperature and/orpressure to optimize a quality of discharge (V-I) characteristic and tocontrol electrical breakdown limit.
 45. (canceled)
 46. (canceled) 47.(canceled)
 48. (canceled)
 49. (canceled)
 50. (canceled)